Iodine is a natural element present in seawater and in some rocks and sediments. There is a non-radioactive and radioactive form of Iodine. Iodine is used as a disinfectant for cleaning surfaces and other objects, in dermatological soaps and bandages, and for cleaning water. Iodine is also added to table salt to ensure that all people receive enough Iodine in their diet. The most radioactive Iodine is man-made. It is used in medical examinations and for the treatment of certain diseases. Most radioactive forms of Iodine are converted very rapidly (from seconds to days) to non-radioactive stable elements. However, 129I converts very slowly (after millions of years). Iodine is a natural ingredient essential for maintaining health. Exposure to high levels of stable or radioactive Iodine can cause thyroid damage.
How does Iodine enter the environment?
The main source of non-radioactive Iodine is seas. It enters the air by seawater droplets or as Iodine gas. When in the air, Iodine can be combined with water or air particles and can enter the soil and surface water and plants when these particles fall to the ground or when it rains. Iodine can remain in the soil for a long time. It can also be absorbed by some plants that grow in the soil, but plants are generally considered a poor source of dietary Iodine.
Small amounts of radioactive Iodine are produced by the operation of nuclear power plants and can be released into air and water. Larger amounts of radioactive Iodine are rarely released and only happen during accidents and atomic bomb explosions. Large quantities of radioactive Iodine are produced in nuclear power plants for medical use. When given to the patient, part of the radioactive Iodine breaks down in the body. The rest is exhaled or excreted in the urine and is naturally broken down in the environment.
How is someone exposed to Iodine?
- The general population is exposed to low levels of Iodine in the air and in certain foods and beverages. Foods (iodized salt, seawater, bread, and dairy products) are the major source of exposure to Iodine.
- The general population is rarely exposed to radioactive Iodine unless subjected to certain medical examinations or given treatment for thyroid diseases.
- People working in plants using radioactive Iodine may be exposed to higher than normal levels.
How can Iodine affect health?
Iodine is an essential element of life. It is required for the synthesis of thyroid hormones, thyroxine, and triiodothyronine (T3 and T4 respectively, their name deriving from the number of Iodine atoms). Iodine deficiency leads to reduced production of T3 and T4 and consequent swelling of the thyroid tissue in an attempt to recruit more Iodine, resulting in a disease known as simple goiter. The main form of thyroid hormone in the blood is thyroxine (T4), which has a longer half-life than T3. In humans, the ratio of T4 to T3 released in the blood is between 14:1 and 20:1. T4 is converted to active T3 (3-4 times more potent than T4) inside the cells with the help of enzymes called deiodinases. Deiodinases are selenium-containing enzymes and therefore dietary selenium uptake is essential for T3 production.
Thyroid tissue and thyroid hormones contain from 15 to 20 mg of Iodine, but 70% of all Iodine in the body is found in other tissues, including the mammary glands, eyes, gastric mucosa, fetal thymus, cerebrospinal fluid and choroid plexus, artery walls, cervix, and salivary glands. Iodine action on the mammary gland is associated with fetal and neonatal development, but in other tissues, its function is unknown.
The recommended daily dietary intake is between 110 and 130 µg for infants up to 12 months, 90 µg for children up to eight years, 130 µg for children up to 13 years, 150 µg for adults, 220 µg for pregnant women, and 290 µg for lactating women. The highest intake level for adults is 1.100 µg/day (1.1 mg/day). The upper tolerable level was assessed by analyzing the effect of the supplements on the thyroid gland without taking into account the upper tolerable limit for absorption into other body tissues, such as mammary tissue in women or prostate tissue in men.
The thyroid gland does not need more than 70 µg/day to synthesize the required amounts of T4 and T3. The highest recommended daily levels of iodine intake appear necessary for the optimal functioning of a number of body systems, including mammary glands, of the gastric mucosa, salivary glands, brain cells, choroid plexus, oral mucosa, and arterial walls.
Natural sources of dietary Iodine include seafood, such as fish, algae, shellfish, dairy products, and eggs if the animals received enough Iodine, and plants grown in Iodine-rich soils. The iodized salt is enriched with Iodine in the form of sodium iodide.
Following the application of Iodine uptake enhancement programs such as iodization of cooking salt, some cases of hyperthyroidism caused by Iodine (Jod-Basedow phenomenon) have been observed. The condition mainly occurs in people over 40 and the risk is higher when Iodine deficiency is severe and initial Iodine intake is high.
In areas where there is little iodine in the diet, usually in areas far from the sea, Iodine deficiency leads to hypothyroidism, the symptoms of which are excessive fatigue, bronchocele, mental retardation, depression, weight gain, and low body temperature. Iodine deficiency is the leading cause of preventable mental disability, an effect that occurs mainly when infants or young children have hypothyroidism by Iodine deficiency. Adding iodine to table salt has largely eliminated this problem, but Iodine deficiency remains a serious public health problem in the developing world today.
Elemental Iodine (I2) is toxic if swallowed. Excess iodine may be more cytotoxic in concomitant selenium deficiency. The toxicity of Iodine is due to its oxidizing properties, which cause the denaturation of proteins (including enzymes).
Elemental Iodine is also a skin irritant and direct contact with the skin can cause damage.
Some people develop hypersensitivity to Iodine-containing products and foods. Applications of tincture of Iodine or Betadine can cause rashes, sometimes severe. Parenteral use of Iodine-based contrast agents can also cause reactions ranging from a mild rash to fatal anaphylaxis. In fact, these reactions are not due to a real allergy to elemental Iodine or Iodine salts, but they are hypersensitivity reactions to other molecular components of foods or preparations.
How does Iodine affect children?
Iodine is essential for the development of children. However, children are more susceptible to the deleterious effects of excessively high levels of stable and radioactive Iodine than adults because their thyroid gland is still developing. If babies and children receive large amounts of Iodine, they may develop an enlarged thyroid gland (bronchocele), which does not produce enough thyroid hormones for normal growth. Radioactive Iodine in foods can be more harmful to babies and children than to adults.
How can the risk of exposure to Iodine be reduced?
Iodine is essential for maintaining health and growth, but (as with all elements) one must prevent exposure to high doses. Foods are not normally expected to contain enough Iodine to cause damage to health. Generally, there should be no concern of over-exposure unless there is exposure to radioactive waste.
How can one determine if one has been exposed to Iodine?
There are two types of tests. One is to check if there is exposure to high doses of radiation and the other is to check if (and how much) Iodine is present in the body. The first type of test looks for changes in blood cells or chromosomes, but it is not possible to determine whether the radiation is from Iodine. The second type of test includes blood, stool, urine, and saliva tests.
We can measure Iodine levels in the blood and most biological materials.
Determination of metals is done by ICP-MS (Inductively Coupled Plasma Mass Spectrometry), a method that enables the simultaneous detection of many metals. Its sensitivity and accuracy are significantly better than conventional atomic absorption, with the ability to measure metals at concentrations up to 1 in 1015 (1 in 1 quadrillion, ppq)!
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. The correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings, and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
At Diagnostiki Athinon we answer any questions you may have about the test you perform in our laboratory and we contact your doctor to get the best possible medical care.